Why don't shotgun slugs and shot use full metal jackets and why

Winchester Super X 12 Gauge Rifled Slug 2.75 1 oz. 1600 FPS

What shotgun shells do the police use? - Quora

Why don't shotgun slugs and shot use full metal jackets and why don't other guns use plastic casings? I believe shotgun shells were originally full metal. - Quora

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Are shotguns bad against armor in general (metal and kevlar) and that's why they're not used in military combat? - Quora

Why are driving bands used for bullets larger than 50 cal? Why aren't driving bands used on all bullets if it is to save material? - Quora

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In Full Metal Jacket, you can see that PVT Pyle has been

Why are shotgun rounds just metal balls? - Quora

Why don't they make pointed shotgun slugs? - Quora